Field of the Invention
The present invention relates to a colored microlens array and a method of manufacturing the same array, and more specifically to a colored microlens array suitable for use as color filters for solid-state image sensing devices, color liquid crystal display units, etc.
Description of the Prior Art
An example of prior art solid-state color image sensing devices will be described hereinbelow with reference to FIG. 1A. In the drawing, the device is composed of a silicon substrate 1, optoelectro transducer regions 2, a light shading film 3, an insulating film 4, a first smoothing layer 5, a first color filter layer 6, a second smoothing (or intermediate) layer 7, a second color filter layer 8, a third smoothing layer 9, a third color filter layer 10, a fourth smoothing layer 11, and a condenser lens layer 12.
In more detail, each optoelectro transducer region 2 is formed by a silicon photodiode, for instance. When light is allowed to be incident upon the optoelectro transducer region 2 through an image forming lens (not shown), the optoelectro transducer region 2 generates an electric charge according to the quantity (luminous power) of the light allowed to be incident thereupon. A great number of optoelectro transducer regions 2 are arranged in matrix fashion on the surface of the silicon substrate 1 as picture elements (i.e. pixels). Therefore, the optoelectro transducer regions 2 generate electric charges according to the brightness of an image projected upon the image sensing device. In the vicinity of the respective optoelectro transducer regions 2, charge transfer regions (not shown) are formed to transfer the generated charges to a preamplifier (not shown) so that the transferred charges are transformed into electric signals.
On the optoelectro transducer regions 2 and the charge transfer regions, the insulating film 3 formed of aluminum, for instance is laminated via the light shading film 4 in order to prevent light from being allowed to be incident upon the areas other than the optoelectro transducer regions 2. The uneven surface caused by forming aperture portions of the light shading film 3 is buried even by additionally forming the first smoothing layer 5.
On this first smoothing layer 5, the first color (e.g. red) filter layer 6 is formed so as to cover the optoelectro transducer regions 2 for transducing only the red components of light into electricity. This color filter layer 6 is formed by dyeing gelatin red, for instance. On the first color filter layer 6, the second smoothing (intermediate) layer 7 is formed to prevent color mixture between the two adjacent color filter layers 6 and 8 and to smooth the surface thereof.
Further, on the second smoothing layer 7, the second color (e.g. green) filter layer 8 is formed so as to cover the optoelectro transducer regions 2 for transducing only the green components of light into electricity. This color filter layer 8 is formed by dyeing gelatin green, for instance. Similarly, on the second color filter layer 8, the third smoothing (intermediate) layer 9 is formed to prevent color mixture between the two adjacent layers 8 and 10 and to smooth the surface thereof.
Further, on the third smoothing layer 9, the third color (e.g. blue) filter layer 10 is formed so as to cover the optoelectro transducer regions 2 for transducing only the blue components of light into electricity.
This color filer layer 10 is formed by dyeing gelatin blue, for instance. On the third color filter layer 10, the fourth smoothing (intermediate) layer 11 is formed to smooth the surface thereof.
Furthermore, on the fourth smoothing layer 11, the condenser lens layer 12 is formed. The condenser lens layer 12 is a group of microlenses for condensing light projected upon the surface of the solid-state color image sensing device through the image forming lens, onto the respective optoelectro transducer regions (pixels) 2.
In the prior art color image sensing device as describe above, a plurality of the smoothing (intermediate) layers and a plurality of the color filter layers are laminated one upon another so as to form a color filter array, and the microlens layer is formed on the outermost portion thereof. Therefore, the respective color components of light can be condensed upon the respective optoelectro transducer regions, as depicted by the solid lines in FIG. 1B (in which the same reference numerals are retained). Accordingly, it is possible to improve the apparent aperture ratio and thereby increase the light receiving sensitivity.
In the prior art color image sensing device, however, since the color filter array is formed by laminating three sorts of color filter layers, the distance between the microlens layer 12 and the aperture portions of the light shading film 3 is as long as 10, also as shown in FIG. 1B. Consequently, when light allowed to be incident upon the microlens obliquely increases as when a diaphragm (an iris) of a camera is relatively opened, the light converged through the microlens is misaligned from the center of the aperture of the light shading film 3 or further offset from the aperture thereof, as depicted by dashed lines in FIG. 1B, thus reducing the light converging rate upon the optoelectro transducer region 2. In addition, when the condensed light reaches the aperture end of the light shading film 3, the signal charge is mixed with the signal charge of the adjacent optoelectro transducer regions (pixels) and the charge transfer regions, with the result that there exists a problem in that smear is produced.